The present invention relates to an alternating current (AC) generator for use in a vehicle and in particularly to an alternating current (AC) generator for use in a vehicle suited for as an electric power generation apparatus for used in an automobile.
In general, an AC generator for use in a vehicle is constituted by a rotor and a stator. The rotor is constituted a pair of oppositely arranged claw shape magnetic poles in which plural claw portions are formed at tip end portions thereof and a field winding for magnetizing the claw shape magnetic pole. Further, the stator is arranged by setting apart at a predetermined interval and further generates an alternating current (AC) voltage according to a magnetization of the claw shape magnetic pole of the rotor.
With the vehicle use AC generator stated in above, since the rotor rotates and a direct current (DC) flows in the field winding, N pole and S pole are generated in the pair of the claw shape magnetic poles. A magnetic flux flown from the claw portion of the claw shape magnetic pole of N pole forms a magnetic circuit in which the magnetic flux passes through a stator iron core of the stator and returns to the claw portion of the claw shape magnetic pole of S pole. In this time, since the magnetic flux of the magnetic circuit intersects the stator winding of the stator, an alternating current (AC) induction voltage generates to the stator winding.
In the vehicle use AC generator stated in above, a magnetic flux amount which intersects the stator winding gives an influence on the electric power generation current. Therefore, in the conventional vehicle use AC generator, a permanent magnet is arranged between the claw portions of the claw shape magnetic pole and the magnetic flux which is formed by the field winding is increased, accordingly the magnetic flux amount which intersects the stator winding is increased.
Further, in the conventional vehicle use AC generator, for example as described in Japanese application patent laid-open publication Nos. Hei 4-251553 and Hei 7-312854, not to fly out the permanent magnet which is arranged between the claw portions of the claw shape magnetic pole according to a centrifugal force caused by the rotation of the rotor, a fly-out prevention member (a non-magnetic material body protection cover) is arranged at the most outer peripheral portion of the claw shape magnetic pole.
However, in the conventional vehicle use AC generator apparatus described in Japanese application patent laid-open publication No. Hei 4-251553, using the non-magnetic material body protection cover, the fly-out of the permanent magnet can be prevented, however since it is necessary to arrange directly plural permanent magnets between the claw shape magnetic poles, respectively, a working operation lowers.
Against to the above stated conventional vehicle use AC generator structure, another type vehicle use AC generator structure is shown, for example described in Japanese application patent laid-open publication No. Hei 3-265450, namely in the AC generator a permanent magnet is arranged between the claw portions of the claw shape magnetic pole and further a protection cover of a non-magnetic material body is arranged only an outer peripheral face of the permanent magnet. This protection cover uses both as the fly-out prevention of the permanent magnet and the holding of the permanent magnet.
However, in the vehicle use AC generator shown in Japanese application patent laid-open publication No. Hei 3-265450, the fly-out prevention member of the permanent magnet uses also the holding of the permanent magnet, since it is necessary to arrange the fly-out prevention member in the outer peripheral portion of the permanent magnet and also in an inner periphery side of the claw shape magnetic pole, a size of the permanent magnet is restricted and becomes small. As a result, since the increase magnetic field operation of the magnetic flux by the provision of the permanent magnet becomes small, there is a problem in which an improvement of an electric power generation efficiency is not hoped so much.
Further, Japanese application patent laid-open publication No. Hei 7-15929 discloses in which, in a claw shape magnetic pole itself of an alternative current (AC) generator for used in a brushless motor, using an austenitic system stainless steel, a portion between the claw shape magnetic poles is non-magnetic material body processed according to a thermal processing.
However, in the above stated Japanese application patent laid-open publication No. Hei 7-15929, the claw shape magnetic pole itself is formed using the austenitic system stainless steel, to make small the leakage magnetic flux since a thickness of the austenitic system stainless steel is necessary to have 5 mm degree, since a large output of a laser to be used is required, an equipment becomes large. Further, when a thin plate is used, there is a problem in which the leakage magnetic flux between the claw shape magnetic poles increases. Further, as the vehicle use AC generator, when it is left as it is at a cold district there is an afraid that a non-magnetic portion returns to the magnetic pole body.